College of Environmental Science and Engineering, Hunan University, Changsha 410082, P.R. China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, P.R. China.
College of Environmental Science and Engineering, Hunan University, Changsha 410082, P.R. China; Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha 410082, P.R. China.
Water Res. 2021 Feb 1;189:116645. doi: 10.1016/j.watres.2020.116645. Epub 2020 Nov 16.
Poly ferric sulfate (PFS), one of the typical inorganic flocculants widely used in wastewater management and waste activated sludge (WAS) dewatering, could be accumulated in WAS and inevitably entered in anaerobic digestion system at high levels. However, knowledge about its impact on methane production is virtually absent. This study therefore aims to fill this gap and provide insights into the mechanisms involved through both batch and long-term tests using either real WAS or synthetic wastewaters as the digestion substrates. Experimental results showed that the maximum methane potential and production rate of WAS was respectively retarded by 39.0% and 66.4%, whereas the lag phase was extended by 237.0% at PFS of 40 g per kg of total solids. Mechanism explorations exhibited that PFS induced the physical enmeshment and disrupted the enzyme activity involved in anaerobic digestion, resulting in an inhibitory state of the bioprocess of hydrolysis, acidogenesis, and methanogenesis. Furthermore, PFS's inhibition to hydrogenotrophic methanogenesis was much severer than that to acetotrophic methanogenesis, which could be supported by the elevated abundances of Methanosaeta sp and the dropped abundances of Methanobacterium sp in PFS-present digester, and probably due to the severe mass transfer resistance of hydrogen between the syntrophic bacteria and methanogens, as well as the higher hydrogen appetency of PFS-induced sulfate reducing bacteria. Among the derivatives of PFS, "multinucleate and multichain-hydroxyl polymers" and sulfate were unveiled to be the major contributors to the decreased methane potential, while the "multinucleate and multichain-hydroxyl polymers" were identified to be the chief buster to the slowed methane-producing rate and the extended lag time.
聚合硫酸铁（PFS）是一种典型的无机絮凝剂，广泛应用于废水管理和剩余活性污泥（WAS）脱水领域，其在 WAS 中会积累并不可避免地在高水平下进入厌氧消化系统。然而，关于其对甲烷生产影响的知识实际上是空白的。因此，本研究旨在填补这一空白，并通过使用实际的 WAS 或合成废水作为消化底物的批处理和长期测试，深入了解相关机制。实验结果表明，在 PFS 为每公斤总固体 40 克的条件下，WAS 的最大甲烷潜力和产率分别延迟了 39.0%和 66.4%，而滞后时间延长了 237.0%。机制探索表明，PFS 导致物理缠结并破坏了参与厌氧消化的酶活性，导致水解、产酸和产甲烷的生物过程处于抑制状态。此外，PFS 对氢营养型甲烷生成的抑制作用比乙酸营养型甲烷生成的抑制作用更为严重，这可以从 PFS 存在的消化器中 Methanosaeta sp 的丰度增加和 Methanobacterium sp 的丰度下降得到支持，这可能是由于氢在共生细菌和产甲烷菌之间的传质阻力较大，以及 PFS 诱导的硫酸盐还原菌对氢的较高食欲所致。在 PFS 的衍生物中，“多核多链羟基聚合物”和硫酸盐被揭示是降低甲烷潜力的主要贡献者，而“多核多链羟基聚合物”被确定是减缓甲烷产生速率和延长滞后时间的主要原因。
